G-5600 Rotor Problem

I am in the process of fixing a 7-year-old G-5600 rotor from the
club station of the Henry Ford Community College ARS, K8EEH.
This is the first time we've had that thing apart.
The elevation rotor will only turn downward; attempting to
raise the antennas would only cause the rotor to "buzz" with no
movement. The rotor motor will only spin in one direction, like
a ratchet, only without the "clicking" noise. This was verified both
mechanically (by spinning the motor, unpowered) and electrically
(by connecting it to the rotor control).
Is the unpowered motor supposed to spin freely in both directions?
What may be the problem? Any suggestions are welcome.
Mike, N8MR
n8mr@amsat.org
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